Electrical contact assembly with permanent magnet blowouts

ABSTRACT

A pair of disc-shaped permanent magnets are held in complementary recesses on opposite sides of an insulating contact block by respective contact arms which carry stationary contacts. Direct current arcs formed when a bridging contact separates from the stationary contacts are driven by the magnets in opposite directions with roots of the arcs moving along respective conductive rims surrounding the magnets.

United States Patent [72] Inventor David L. Swindler Northfield, Ohio [2]] App]. No. 791,951

[22] Filed Jan. I7, 1969 [45] Patented July 20, I971 [73] Assignee Square D Company Park Ridge, Ill.

[54] ELECTRICAL CONTACT ASSEMBLY WITH PERMANENT MAGNET BLOWOUTS 6 Claims, 4 Drawing Figs.

[52] U.S.CI 200/147 A [51] Int. Cl ...H0lh 33/18 [50] FieldotSearch 200/147 A, 147

[5 6] References Cited UNITED STATES PATENTS 2,153,402 4/l939 Tritle 200/l47(A) Primary Examiner-Robert S. Macon Attorneys-Harold J. Rathbun and Richard T. Guttman ABSTRACT: A pair of disc-shaped permanent magnets are held in complementary recesses on opposite sides of an insulating contact block by respective contact anns which carry stationary contacts. Direct current arcs formed when a bridging contact separates from the stationary contacts are driven by the magnets in opposite directions with roots of the arcs moving along respective conductive rims surrounding the magnets.

ELECTRICAL CONTACT ASSEMBLY WITH PERMANENT MAGNET BLOWOUTS This invention'relates to a stationary contact assembly for use in a direct current contactor or relay, and more particularly to such a contact assembly having permanent-magnet blowouts.

Two of the disadvantages in the use of permanent magnets as blowout means or blowouts for direct current relays or contactors have been the difficulty of mounting the magnets adjacent the contacts and of providing guards or'arc runners which insure that arcs do not play upon the magnets. These disadvantages are overcome in the present stationary contact assembly by securing disc-shaped magnets on opposite sides of a web portion of a contact block by spring action of respective contact arms which carry stationary contacts positioned ad jacent the periphery of the magnets, and by securing rims of good arc-resistant metal around the magnets so that if arc roots leave the stationary contacts they transfer from the contacts to the metal rims.

it is an object of this invention to provide an improved stationary contact assembly including permanent magnet blowouts.

A further object is to provide a stationary contact assembly having disc-shaped permanent magnets for blowout purposes held in place on a contact block by respective stationary contact arms secured to the contact block.

Another object is to provide a stationary contact assembly including a disc-shaped permanent magnet positioned to control movement of an arc and surrounded by a rim of electrically conductive and arc-resistant metal.

Further objects and advantages of this invention will become apparent from the following specification wherein reference is made to the accompanying drawings, in which:

FIG. I is a side elevation of a stationary'contact assembly in accordance with this invention;

F IG. 2 is a front elevation of the contact assembly of FIG. 1;

FIG. 3 is a bottom view of the contact assembly of FIG. 1', and

FIG. 4 is an exploded perspective view of the contact assembly of FIG. I viewed generally from the bottom front thereof.

A stationary contact assembly in 'accordanccwith this invention comprises a support or contact block l'molded of hard and dense insulating material and having, in opposite sides of a front portion thereof, a pair of recesses 11 and 12 which define an intermediate web portion 14 and respective overhanging upper wall portions 15 and 16. At the rear portions of the recesses 11 and 12 are respective stepped portions 18 and 19 defining respective front-facing semicircular surfaces 20 and 21 positioned inwardly and forwardly of respective front-facing plane surfaces 24 and 25. Midway of their length, the semicircular surfaces 20 and 21 have respective small protuberances 27, only one of which is shown, and the surfaces 24 and 25 have respective transverse notches 28and 29.

Opening at their forward ends in the bases of the notches 28 and 29, respectively, are relatively small holes 30 extending through a rear portion 31 of the block 10 and opening at their rearward ends in respective recesses 32 formed in opposite sidewalls of the rear portion 31, only one of the holes 30 and one of the recesses 32 being shown. Bottom walls 33 of the respective recesses 32 are sloped downwardly to prevent dust accumulation. Opening at their forward ends in the respective surfaces 24 and 25 below the notches 28 and 29 are relatively large holes 34 and 35 extending through the rear portion 31 and opening at their rearward ends at a rear surface 36 'of the block 10. The holes 34 and 35 are of larger diameter at their front end portions than at their rear end portions thereby to define respective annular shoulders 38 and 39.

The stationary contact assembly also includes a pair of identical contact arms 40. Each of the contact arms 40'has a straight intennediate portion 41 with an inwardly turned contact-carrying portion 42 at one end. At the other end of the intermediate portion 41, each contact'arm40'has a Z-shaped portion including an outwardly turned mounting portion'44 and an outwardly turned terminal portion 45. Each portion 42 carries a'stationary contact 46, and each'portion 45 has a U- shaped wire clamp or terminal 48 secured thereto as by a screw 49 threaded into an opening in the portion 45. Centrally of each intermediate portion 41 is an inwardly directedprotuberance 50 and centrally of each portion 44is a hole receiving a screw 5 I.

For controlling arcs formed at the contacts 46 in a manner to be described, the contact assembly includes a pair of identical disc-shaped circular permanent magnets 52, opposite side faces of each of which are of opposite polarity. The magnets 52 are formed preferably of a rubber-bonded barium ferrite composition, and each has a cylindrical axial recess 54 at least on one side. If desired, each recess 54 may be an end portion of an axial hole extending through the magnet 52. Snugly received about the periphery of each magnet 52 is a split rim 55 made of nonflux-conducting metal having good arc-resistant properties such as copper, a copper alloy, or aluminum. The rims 55 have a normal inner diameter less than the diameter of the magnets 52 and are resilient so as to be frictionally held in position when assembled on the respective magnets 52 'with spaces 56 between the split ends.

The assembled magnets 52 and rims 55 are placed in the respective recesses 11 and 12 with the rims 55 bearing against the surfaces 20 and 21 and with the protuberances 27 withing the spaces 56 between the ends of the rims thereby to prevent rotation of the rims. Preferably, the outer side surfaces of the magnets 52 are at an angle of with respect to the bases of the respective notches 28 and 29 and the portion 41 of each contact arm 40 before assembly is at an internal angle of more than 90 with respect to the mounting portion 44. Thus, when the contact arms 40 are secured to the contact block 10 by reception of the portions 44 in the respective notches 28 and 29 and by reception of the screws 51 in the respective openings 30, nuts 57 being tightened on the rear ends of the screws 51, the resiliency of the contact arms 40 and reception of the protuberances50 into the respective recesses 54 maintains the respective magnets 52 in position and insures that there is a good electrical connection between the contact arms 40 and the respective rims 55.

The contact assembly may be mounted on a panel by means of a pair of screws 58 received in the openings 34 and 35 respectively, and having their head portions bearing against the annular shoulders 38 and 39 with intervening lockwashers.

In operation, when direct current power is supplied at the terminals 48 and a reciprocative contact bridge 59 (FIG. 3) carrying spaced contacts 60 separates from the contacts 46, arcs are formed across the intervening contact gaps. Preferably, the polarity of the magnets 52 and the magnetic fields provided thereby are such that the arc bridging one of the contact gaps is moved upwardly while the arc bridging the other contact gap is moved downwardly. The consequent lengthening of the arcs is ordinarily sufficient to extinguish the arcs. If desired, both arcs could be driven upwardly or both downwardly by proper selection of magnet polarity.

Extinguishment of the arcs is also facilitated by the rims 55 which, as previously described, are electrically connected to the contact arms 40. In the normally open configuration of the contact assembly as illustrated in the drawings, the roots of intense arcs on the stationary contacts 46 transfer to their respectiveadjacent rims 55 and are moved along the rims in the respective directions previously mentioned, thereby to facilitate a prompt interruption of the arcs and, additionally, to minimize erosion of the contacts 46.

Althoughthe contact bridge 59 is shown as positioned in front of the contacts 46, it is apparent that the contact arms 40 could be longer with the contacts 46 facing'the magnets 52 and the contact bridge 59 positioned for reciprocation between the contacts 46 and the magnets 52.

What I claim is:

tromagnetic relay comprising an insulating contact block, a

pair of disc-shaped permanent magnets disposed in coaxially aligned spaced-apart relationship at opposite sides of the block, respectively, a pair of stationary contacts disposed in radial alignment with, and in closely spaced relation to, the peripheries of the magnets, respectively, and a movable contact bridge to selectively make'and break a circuit between said pair of stationary contacts.

2. A contact assembly as claimed in claim 1 wherein the opposite side faces of each magnet are of opposite polarity.

3. A contact assembly as claimed in claim 2 and additionally including a pair of rims of electrically conductive, nonfluxconducting, arc-resistant material, said rims being assembled on the respective magnets about the peripheral surface thereof, respectively.

4. A contact assembly as claimed in claim 3 wherein the contact block has recesses in opposite sides, respectively, each recess has a curved wall surface complementary to a portion of the peripheral surfaces of said rims, and the assembled magnets and rims are received in said recesses, respectively, with the complementary surfaces in contact.

5. A contact assembly as claimed in claim 4 wherein said contacts are carried by a pair of resilient contact arms secured to said contact block on opposite sides thereof and overlying the magnets, respectively, the magnets being held in the recesses by spring action of the contact arms with the contact arms in electrical connection with the rims.

6. A contact assembly as claimed in claim 5 wherein said magnets have axial recesses in their outer side faces, respectively, and said contact arms have bosses, respectively, received in said recesses.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. I 3,594,526 DA E July 20, 1971 |NV ENTOR( 1 David L. Swindler It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 29, "withing' should read -within--.

The references cited in the prosecution of the application on which this patent is based should read as follows:

UNITED STATES PATENTS 2,153,402 4/1939 Tritle 200/147 (A) 2,571,951 10/1951 Sohaelchlin 200/147(A) 2,875,303 2/1959 Immel et al 200/147 3,064,104 11/1962 Wells et al 200/ 147(A) FOREIGN PATENTS 998,482 7/1965 Great Britain 200/147(A) Signed and Scaled this rim Day Of November 1977 [SEAL] RUTH C. MASON LUTRELLE F. PARKER Arresting Oflicer Acting Commissioner of Patents and Trademarks 

1. A contact assembly for use in a direct current electromagnetic relay comprising an insulating contact block, a pair of disc-shaped permanent magnets disposed in coaxially aligned spaced-apart relationship at opposite sides of the block, respectively, a pair of stationary contacts disposed in radial alignment with, and in closely spaced relation to, the peripheries of the magnets, respectively, and a movable contact bridge to selectively make and break a circuit between said pair of stationary contacts.
 2. A contact assembly as claimed in claim 1 wherein the opposite side faces of each magnet are of opposite polarity.
 3. A contact assembly as claimed in claim 2 and additionally including a pair of rims of electrically conductive, nonflux-conducting, arc-resistant material, said rims being assembled on the respective magnets about the peripheral surface thereof, respectively.
 4. A contact assembly as claimed in claim 3 wherein the contact block has recesses in opposite sides, respectively, each recess has a curved wall surface complementary to a portion of the peripheral surfaces of said rims, and the assembled magnets and rims are received in said recesses, respectively, with the complementary surfaces in contact.
 5. A contact assembly as claimed in claim 4 wherein said contacts are carried by a pair of resilient contact arms secured to said contact block on opposite sides thereof and overlying the magnets, respectively, the magnets being held in the recesses by spring action of the contact arms with the contact arms in electrical connection with the rims.
 6. A contact assembly as claimed in claim 5 wherein said magnets have axial recesses in their outer side faces, respectively, and said contact arms have bosses, respectively, received in said recesses. 